Table of Contents

  • TRANSFORMATION OF HETEROPHASE NON-METALLIC INCLUSIONS “HIGHMELTING PHASE SURROUNDING WITH LOW-MELTING COVER” IN STEELS UNDER LASER ACTION

    pg(s) 121-125

    Melting and crystallization of heterophase non-metallic inclusions “high-melting phase surrounding with low-melting cover” was investigated. It was shown that under laser action the initial structure of inclusion-steel matrix boundaries transits into unstable equilibrium high-energy condition that cause development of the dissipation processes connecting with aspiration of system inclusionmatrix to the state with minimum of free energy. In the result of the system heterophase inclusion-matrix transits to the state of unstable equilibrium which determines structure and properties of laser-quenched interphase boundary. Processes of melting, fusion and dissolution of non-metallic inclusions “high-melting phase surrounding with low-melting cover” and also of the melting of steel matrix play the great role in transformation of interphase inclusion-matrix boundaries under laser action.

  • ANALYSIS OF THE GRAIN BOUNDARY MICROSTRUCTURE AND DEGRADATION IN A GAS TURBINE BLADE

    pg(s) 126-129

    We studied the different parts (lock and feather) of Inconel 738C gas turbine blade, which were cut from the working turbine blade after long operation and recovery heat treatment. Undesired phases such as TCP phase (sigma phase) and some of continuous carbides such as M23C6 in the grain boundary are found. The presence of M23C6 carbides in studied samples testifies to the diffusion process of decomposition of MC carbide and the associated softening of the alloy. The appearance of sigma phase leads to embrittlement of the alloy. Generation of these specifications in the structure results in degradation of metallurgical and mechanical properties of the blade and eventually its destruction.

  • THE IMPACT OF CURRENT SHAPE DURING THE CONSOLIDATION PROCESS ON PHYSICO-MECHANICAL PROPERTIES OF FUNCTIONAL Fe – Ti – C – B SYSTEM MATERIALS

    pg(s) 130-133

    The impact of current shape during consolidation of Fe – Ti – C – B system materials on the physio-mechanical properties of obtained specimens is studied in present paper. It is experimentally found that the use of method of decrease of voltage surge on output Schottky diodes of SPS device and the decrease of operation time of overcurrent protection in power circuit of SPS generator allowed changing current harmonic composition which lead to an increase of properties of consolidated Fe – Ti – C – B specimens – porosity decreased from 15.8 to 2.8 %, hardness increased from 50 to 55 HRC, loss of mass during abrasive wear decreased from 2 to 0.5 mass. %, and bending strength increased from 750 to 1500 MPa. It is found out that increase of input power during consolidation from 1.3 to 7.5 kJ/s by changing current harmonic composition leads to an increase of physico-mechanical characteristics of Fe – Ti – C – B system metalmatrix composites. Density of consolidated specimens increased from 75 to 95 %, their hardness increased from 35 to 50 HRC, loss of mass during abrasive wear decreased from 10 to 1 mass. % and their bending strength increased from 400 to 1100 MPa.

  • EVOLUTION OF PHASES AT THE BIFURCATION POINT

    pg(s) 134-136

    In chemical reactions, the bifurcation points are determined through the triangulation of the system. In the interaction of the components, bifurcation sequence formed and the system evolves along one of them to form a stable compound. The transformations of the components at the bifurcation point are determined basis on the "The Gibbs function normalized to the total number of electrons". All transformations are described through chemical potential, affinity, thermodynamics force. Calculated the production of entropy, the entropy flux and the reaction rate constant, which allowing the system to choose a certain path of evolutionary transformations.

  • NONCONVENTIONAL METHODS OF HEAT TREATMENT OF ALUMINUM ALLOYS

    pg(s) 137-140

    This paper presents new methods of thermal processing of the aluminum alloys. It analyses the effects of boiling treatment of alloys Al–Cu and Al–Si in an oxidizing atmosphere on their microstructure, hydrogen content and the coefficient of linear thermal expansion (CLE). An increase of boiling time from 15 to 75 hours results in an initial increase in the hydrogen content in alloys later followed by a decline in the hydrogen content. These changes in the hydrogen content correlate with the dynamics of alloys’ microstructure and their CLE. This study shows that atmosphere with a high oxygen content induces an acceleration of diffusion processes in aluminum alloys. If boiling time does not exceed 30 hours, the hydrogen content in a solid solution and etchability of grain boundaries of α-solid solution decrease and intermediate phases get partially dissolved. We demonstrate that boiling treatment of aluminum alloys in an oxidizing atmosphere leads to a decline of the CLE measured under the temperature 50-450°С which is especially strong when measured under the temperature 250-350°С.

  • THE STRUCTURAL AND TOPOLOGICAL HEREDITARITY UPON CRYSTALLIZATION OF NEAR-EUTECTIC ALLOYS

    pg(s) 141-145

    A new representation of a heterogeneous long-range ordered structure of metal melts consisting of "liquid" and "solid" component atoms mixture has been formulated. The elements of a super-high level structure that are directly associated with a quasicrystalline liquid phase structure have been revealed. Like any solid, they are caused by distortion of long-range order in its "quasilattice" made up by "liquid" component atoms at the temperatures exceeding their melting point. Upon crystallization, these structural elements convert excess phases dendrites into macroscopic spherical formations that reflect a "polygrain" melt structure, its topology, and unique "genetic code" acquired during the transfer of layout topological hereditary information from a melt to a solid.

  • MAGNETIC AND ELECTROCONDUCTIVE PROPERTIES OF THE PURE CARBON SOOT SYNTHESISED BY ARC DISCHARGE

    pg(s) 146-149

    The electroconductive and magnetic properties of nanomaterials containing carbon nanoforms synthesised for electrocatalytic, electrochromic, and ferrofluid applications, etc., are of interest to researchers. This article aims to understand the physical effects influencing the electroconductive and magnetic properties of materials synthesised by arc discharge. The nanomaterial formation processes leading to the formation of magnetic and electroconductive structures are also discussed. Arc discharge between graphitic electrodes results in the emergence of a fan-shaped jet of helium and carbon. The gasdynamic and temperature parameters of the jet depend on the parameters of the arc discharge and the buffer gas. Variations in the parameters of the carbon vapour flow change the kinetics of carbon condensation, leading to variations in the morphology and structure of the carbon material. The main external parameter of the synthesis (buffer gas pressure) was varied in the study, and correlations between the intensity ratio of the D to G peaks on the Raman spectrum and the electrical conductivity and magnetic susceptibility values were found. During the synthesis, nanographite structures were formed. However, the formation of an amorphous carbon structure on the free ‘zig-zag’ edges of the graphite fragments reduced the magnetic susceptibility, the electrical conductivity and the ID/IG ratio.

  • MODELING OF METAL CRYSTALLIZATION BY MEANS OF CELLULAR AUTOMATON

    pg(s) 150-153

    Simulation model of crystallization, which is based on combination of mathematical modeling methods and a probabilistic cellular automaton, is presented here. Such combination makes it possible to predict process of metals and alloys structure formation whiles crystallization under various cooling conditions, and also to study this process both in the course of homogeneous and heterogeneous nucleation.

  • STUDY OF PHASE TRANSFORMATIONS IN THE ROLLS OF ALLOY STEELS DURING QUENCHING BASED ON FINITE-ELEMENT MODEL

    pg(s) 154-157

    The studies are represented of phase and structure transformations during the process of multi-stage heat treatment of large-scale rolls. Adapted analytical models are introduced and applied to the calculation of phase transformations together with the finiteelement models of rolls. The results show phase components distribution over the hardened layer of rolls of the special alloy steels 50CrMnMoV and 45Cr3MnNiMoV at different stages of the manufacturing process.

  • EFFECT OF INITIAL MOLD TEMPERATURE ON THE CRYSTALLIZATION KINETICS OF Cu47Ni8Ti34Zr11 ALLOY

    pg(s) 158-160

    Using the method of mathematical modeling, the effect of the initial temperature of the mold on the thermal conditions and kinetics of crystallization of chill castings of Cu47Ni8Ti34Zr11 alloy was investigated. According to the results, established that the value can have a significant effect on the final structure of the ingots. Depending on the value of, it is possible to provide thermal conditions under which formation of amorphous, amorphous-crystalline and fully crystalline states is possible. It is shown that the changes in the initial temperature of the mold are reflected in the final parameters of the microstructure of the resulting ingots, the average crystal size can vary from tens of nanometers to several micrometers.

  • EFFECT OF HIGH PRESSURE TORSION ON THE STRUCTURE, MICROHARDNESS AND HEATING BEHAVIOUR OF THE MAGNESIUM ALLOY WE43

    pg(s) 161-164

    In the present work, the magnesium alloy WE43 (Mg-Y-Nd-Zr) after high pressure torsion (HPT) was investigated. HPT was conducted at room temperature, 200 °C or 300 °C. As a result of HPT processing, a large number of twins with the twin size of 0.4 − 8.1 µm were formed. Furthermore, the HPT process led to the formation of a very fine grain structure with the average grain size of 30 – 100 nm. The deformation by HPT caused the formation of a displaced basal texture, which sharpens with an increase in the deformation temperature. The refinement of the microstructure brought about an improvement of the microhardness of the alloy over the as-received condition. The microhardness after HPT at the room temperature increased up to 1189 ± 33MPa compared with 774 ± 50 MPa in the initial state. A subsequent aging after HPT led to an additional strengthening to a level of 1411 ± 40 MPa. It was noted that thermal stability of strengthening caused by HPT did not depend on the deformation temperature and sustained up to 250 °C.

  • CORROSION PROPERTIES OF DIFFUSIONAL ZINC COATINGS OBTAINED BY NANOGALVANIZING

    pg(s) 165-166

    Corrosion properties of diffusional zinc coatings with various surface compositions, obtained by nanogalvanizing technology, are studied in model oilfield and aggressive chloride-containing media. A complex of physical and chemical methods for studying corrosion behavior, including polarization measurements, X-ray diffraction analysis and SEM, was used in the work. Corrosion resistance of diffusional zinc coatings obtained by nanogalvanizing is determined by the composition, texture and thickness of the coating.